This application is a 35 USC 371 application of PCT/DE 00/03606 filed on Oct. 13, 2000.
1. Field of the Invention
The invention relates to a common rail for a common rail fuel injection system of an internal combustion engine, having a hollow base body that is equipped with a plurality of connection openings, and to a method for producing such a common rail.
2. Description of the Prior Art
In common rail injection systems, a high-pressure pump, optionally with the aid of a prefeed pump, pumps the fuel that is to be injected from a tank into the central high- pressure fuel reservoir, which is called a common rail. From the rail, fuel lines lead to the individual injectors that are assigned to the engine cylinders. The injectors are triggered individually the engine electronics, as a function of the engine operating parameters, in order to inject fuel into the combustion chamber of the engine. By means of the common rail, the pressure generation and the injection are decoupled from one another.
A conventional common rail is described for instance in German Patent Disclosure DE 195 48 611. The conventional common rails withstand pressures of up to about 1100 bar.
The primary object of the invention is to increase the high-pressure strength of the known common rail by simple provisions.
In a common rail for a common rail fuel injection system of an internal combustion engine, having a hollow base body that is equipped with a plurality of connection openings, this object is attained in that the interior of the base body is embodied as flat in the region of the connection openings. Within the context of the present invention, it has been found that the high-pressure strength of the common rail is limited primarily by the intersections between the connection openings and the base body. In operation, peak stresses that can lead to the development of cracks in the base body occur in the intersection region. By the provision according to the invention, the high-pressure strength of the common rail is increased without substantially increasing its structural volume. The interior of the base body can have a cylindrical or spherical geometry, for instance.
One particular embodiment of the common rail of the invention is attained in that a connection stub is embodied on the base body and has a connection bore whose center line is disposed perpendicular to an internal flat face in the region of the connection opening. This offers the advantage that the peak stresses in the intersection region are minimized.
A common rail for a common rail fuel injection system of an internal combustion engine, having a tubular base body that is equipped with a plurality of connection openings, achieves the above-stated object in that the inside diameter of the tubular base body is widened in the region of the connection openings. The pressure strength of the common rail increases if the ratio between the inside diameter of the base body and the inside diameter of the connection openings is selected to be as great as possible. The local widening of the inside diameter of the base body leads to an increase in this diameter ratio in the critical region of the connection openings, without increasing the external dimensions of the common rail of the invention.
A common rail for a common rail fuel injection system of an internal combustion engine, having a tubular base body that is equipped with a plurality of connection openings attains the above-stated object in that the interior of the tubular base body is embodied as flat in the region of the connection openings. This means that the inside diameter of the tubular base body assumes the value of xe2x80x9cinfinitexe2x80x9d in the region of the connection openings. This provision leads to the maximum high-pressure strength of the common rail of the invention, at a minimized structural volume. The connection openings are as a rule formed by radial bores, whose center lines are each disposed perpendicular to the flat face in the region of the connection openings.
In a method for producing a common rail as described above, the above-stated object is attained in that the tubular base body is deformed inward in the region of the connection openings in such a way that it protrudes inward, and that the inward-protruding region is machined in a way that removes material, in order to widen the inside diameter of the tubular base body in the region of the connection openings. By this means, in a simple way, local widening of the inside diameter of the base body only in the region of the connection openings is achieved.
A particular embodiment of the method of the invention is characterized in that the interior of the tubular base body is machined in the region of the connection openings with the aid of an electrochemical removal method (ECM, for Electrochemical Machining). The use of this method has proved itself in practice to be especially advantageous.